400 fps to mph conversion result above is displayed in three different forms: as a decimal (which could be rounded), in scientific notation (scientific form, standard index form or standard form in the United Kingdom) and as a fraction (exact result). Every display form has its own advantages and in different situations particular form is more convenient than another. For example usage of scientific notation when working with big numbers is recommended due to easier reading and comprehension. Usage of fractions is recommended when more precision is needed.
If we want to calculate how many Miles per Hour are 400 Feet per Second we have to multiply 400 by 15 and divide the product by 22. So for 400 we have: (400 × 15) ÷ 22 = 6000 ÷ 22 = 272.72727272727 Miles per Hour
So finally 400 fps = 272.72727272727 mph